The present invention relates to an image sensor which reads picture-information and electrically transmits it, and which is suitable for a facsimile machine or image scanner.
In the prior art linear image sensor IC, the structure of the linear image sensor IC shown in block diagram form in FIG. 3 is known. This structure comprises a light-receiving element array having a plurality of light-receiving elements, a transfer section for receiving outputs of the light-receiving elements and outputting corresponding electric signals, and comprising an analog switch array having a plurality of switches, a shift register operating as a scanning circuit, and a scanning input circuit and a clock buffer for driving the shift register. An output circuit is further provided for outputting an output signal of the scanning circuit and a picture signal received by the light-receiving element.
However, in a contact type linear image sensor of a multi-chip system having a plurality of prior art linear image sensor ICs, the clock buffer always operates even when the picture signal is in storage and is not being output after reading the picture signal out because a clock signal is always input. Therefore, there has been a problem in that the clock buffer operates idly, which consumes 50% or 90% of the total current of the linear imaging process.